Receptor tyrosine kinases are large enzymes that span the cell membrane and possess an extracellular binding domain for growth factors, a transmembrane domain, and an intracellular portion that functions as a kinase to phosphorylate a specific tyrosine residue in proteins and hence to influence cell proliferation. Tyrosine kinases may be classified as growth factor receptor (e.g. EGFR, PDGFR, FGFR and erbB2) or non-receptor (e.g. c-src and bcr-abl) kinases. Such kinases may be aberrantly expressed in common human cancers such as breast cancer, gastrointestinal cancers such as colon, rectal or stomach cancer, leukemia, and ovarian, bronchial or pancreatic cancer. Aberrant erbB2 activity has been implicated in breast, ovarian, non-small cell lung, pancreatic, gastric and colon cancers.
Normal angiogenesis plays an important role in a variety of processes including embryonic development, wound healing and several components of female reproductive function. Undesirable or pathological angiogenesis has been associated with disease states including diabetic retinopathy, psoriasis, cancer, rheumatoid arthritis, atheroma. Tumor angiogenesis, the formation of new blood vessels and their permeability is primarily regulated by (tumor-derived) vascular endothelial growth factor (VEGF), which acts via at least two different receptors: VEGF-R1 (Flt-1); and VEGF-R2 (KDR, Flk-1). The VEGF KDR receptor is highly specific for vascular endothelial cells (Endocr. Rev. 1992, 13, 18; FASEB J. 1999, 13, 9).
A large number of human tumors, especially gliomas and carcinomas, express high levels of VEGF and its receptors. This has led to the hypothesis that the VEGF released by tumor cells stimulates the growth of blood capillaries and the proliferation of tumor endothelium in a paracrine manner and through the improved blood supply, accelerate tumor growth. Direct evidence of the role of VEGF as a tumor angiogenesis factor in vivo is shown in studies in which VEGF expression or VEGF activity was inhibited. This was achieved with anti-VEGF antibodies, with dominant-negative VEGFR-2 mutants which inhibited signal transduction, and with antisense-VEGF RNA techniques. All approaches led to a reduction in the growth of glioma cell lines or other tumor cell lines in vivo as a result of inhibited tumor angiogenesis.
Three principal mechanisms play an important part in the activity of angiogenesis inhibitors against tumors: 1) Inhibition of the growth of vessels, especially capillaries, into vascular resting tumors, with the result that there is no net tumor growth owing to the balance that is achieved between cell death and proliferation; 2) Prevention of the migration of tumor cells owing to the absence of blood flow to and from tumors; and 3) Inhibition of endothelial cell proliferation, thus avoiding the paracrine growth-stimulating effect exerted on the surrounding tissue by the endothelial cells which normally line the vessels.
The present invention is based on the discovery of compounds that surprisingly inhibit the effect of VEGF, a property of value in the treatment of disease states associated with angiogenesis and/or increased vascular permeability such cancer, diabetes, psoriasis, rheumatoid arthritis, Kaposi's, haemangioma, acute and chronic nephropathies, atheroma, arterial restenosis, autoimmune disease, acute inflammation, excessive scar formation and adhesions, lymphoedema, endometriosis, dysfunctional uterine bleeding and ocular diseases with retinal vessel proliferation.
It has now been found that spiro substituted compounds of formula I, described below, are a new class of compounds that have advantageous pharmacological properties and inhibit the activity of protein tyrosine kinases, such as VEGFr, EGFr, c-kit, PDGF, FGF, SRC etc. They may also be irreversible inhibitors of protein tyrosine kinases.
Examples of compounds that are similar in structure to those of the present invention are disclosed in the following literatures: WO9717329, WO9722596, WO0047212, WO2002032872, WO2004018430, WO2005073224, WO2005080377, WO2005097134, WO2005097137, WO2005114219, WO2005070891, WO05021553, WO2005063739.